Fluid cooling of reciprocating piston



T6; '1952"' EE. HATTERTON y 2,621,638I

FLUID COOLING OF RECIPROCATINGPISTON Filed Feb. 2o. 1951 I npenior l l Attorney Patented Dec. 16, 1952 FLUID COOLING oF RECIPROCATING Pis'roN Ernest Edward Chatterton, London, England, as-

signor to D. Napier & Son Limited, London, England, a company of Great Britain Application February zo, 1951, serial No. 211,875 In Great Britain February 28, 1950 9 Claims. 1

This invention relates to pistons of the kind comprising a crown portion and a skirt portion with a ring-carrying portion between them provided with one or more ring grooves, and more particularly to pistons for internal combustion engines designed to operate under high load or other conditions in which the rate of heat now to the piston tends to be high.

In such engines the limit of output may be determined by the maximum temperature to which the piston can be brought without risk of mechanical failure or without affecting adversely conditions Within the combustion chamber or causing the function of the rings to be impaired, as by the rings reaching a temperature at which lubrication between them and the cylinder wall tends to break down or by the formation of excessive carbon in the grooves.

It has Aalready been proposed in our prior United States Patent No. 2,534,573 to provide a piston which is cooled in the neighbourhood of the ring grooves by the action of a heat transfer substance which under the reciprocating motion of the piston is shaken from one end to the other of an adjacently situated chamber. It has also been proposed in the same application to provide a. separate cooling circuit for the piston crown, and the arrangement was designed to minimise any transference of heat by the heat transfer substance from the crown of the piston to the 1,.

ring-carrying portion.

The object of :the present invention is to provide a modified arrangement of this type also aimed at minimising any transference of heat from the crown of the piston to the ring-carrying portion.

According to the present invention a piston of the kind referred to has an annular chamber behind the ring groove or grooves extending towards or into the skirt portion and closed at its lower end, a. crown-cooling chamber extending across the under surface of the piston crown, communieating with the annular chamber through one or more cooling liquid transfer passages and provided with one or more outlets communicat-v ing with the open interior of the piston, and means for delivering heat-transfer liquid from the connecting rod to the annular chamber in such quantity that it will be shaken from end to end of the annular chamber by the reciproca-tion of the piston and surplus liquid will be caused to 2 and for convenience, therefore, will be referred to herein as oil.

Preferably the transfer passage or each transfer passage opens out of the annular chamber at a point in its length such as to limit and determine the quantity of oil maintained in the annular chamber during reciprocation of the piston, that is to say so that the vtransfer passage or passages act as spill ports through which surplus oil covering the ports when the oil is thrown to the upper end of the chamber during each reciprocation of the piston is ejected into the crown-cooling chamber.

The form of the crown-cooling chamber may vary but in a preferred arrangement it comprises an annular channel lying adjacent to the circumference of the piston crown, a central pocket lying adjacent to the centre of the piston crown, and a series of channels extending between the annular channel and the central pocketk and vthrough which the oil is caused to flow in its passage from the transfer passage or passages to the outlet or outlets. In such an arrangement the transfer passage or passages conveniently communicate with the central pocket, while tWo or more outlet passages extend from circumferentially displaced points in the annular channel into the open interior of the piston.

A piston according to the invention may be constructed in various ways but one construction of such a piston is illustrated by way of example iri the accompanying drawings, in which Figure l is a plan view partly in section and partly broken away to show the form of the crown-cooling chamber,

Figure 2 is a sectional side elevation on the line 2-2 of Figure 1, and

Figure 3 is a cross-sectional view on the lineA 3-3 of Figure 1.

In the construction illustrated the piston comprises inner and outer parts A and B, the outer part A being of tubular form and comprising a -K crown A1, a ring-carrying portion A2 provided pass through the transfer passage or passagesV with ring grooves A3 and a skirt portion A4, the ring-carrying portion having an internal diameter which is less than that of the skirt portion, while the skirt portion is provided with an internal flange A5, having a circumferential groove A6 therein.

The inner part B of the piston is of plug-like external form vand is provided internally with a wide diametral web B1 the lower end of which is forked to provide two gudgeon pin bosses B2 to receive the ends of a gudgeon pin C by which the connecting rod D is connected to the piston.

The external formation of the inner part B ls such, as shown, as to form with the portions A2 and A4 of the outer part A an annular chamber E which is closed at its lower end by the flange A5, the inner part B being rigidly secured within the outer part A by an expanding spring ring F engaging the groove A6 in the flange A5 and having a wide angle frusto-conical lower face cooperating with a similar face of the groove so as to exert an upward wedging action on the inner part B.

Formed in the upper face of the inner part B is a crown-cooling chamber comprising an annular channel G lying adjacent to the circumference of the piston crown, a central pocket G1 at the centre of the crown and a series of radial channels G2 connecting the channel G to the Docket G1.

Formed in the web B1 are four oil transfer passages I-l each of which leads from a point somewhat above the middle of the length of the annular chamber E into the central pocket G1, while four outlets J lead from circumferentially displaced points in the channel G into the open interior cf the piston as shown most clearly in Figure 3.

The upper end of the connecting rod D is formed in known manner to make a substantially fluid-tight seal with a part of the web B1 and has oil supply passages D1, D2 formed therein by which oil is fed toa collecting chamber K formed in this web and communicating with the annular chamber E by way of two oil delivery passages K1.

During operation of the piston oil will be delivered either continuously under pressure or intermittently by momentum effects through the pas sages Dl, D?, the chamber K and the passages K1 into the annular chamber E. The oil thus maintained in this chamber will he thrown back and forth between the ends of the chamber by the reciprocation. of the piston, and when, during the last part of each upstrolie of the piston, the oil is thrown into the upper end of the chamber E any surplus oil, that is to say any oil which then lies below the ends of the passages H will be ejected through these passages into the pocket G, thus ejecting a similar quantity of oil from the crown-cooling chamber through the outlets J into the open interior of the piston.

It will therefore be seen that a quantity of oil which is renewed substantially continuously during operation will be shaken back and forth in the chamber thus providing good cooling for the walls of this Chamber, including the ringcarrying part A2, while the surplus oil from this chamber is ejected into the crown-cooling chainber, G1, G2, G where it effects further cooling before being discharged into the open interior of the piston and thence Ending its way into the engine crank case or oil sump. The oil thus provides cooling for the ring carrying part of the piston first and then passes on to the hotter` crown portion whereby satisfactory cooling of the ring carrying part and the extraction by the oil of the maximum quantity of heat tends to be obtained.

What I cla-im as my invention and desire to secure by Letters Patent is:

1. A piston for an internal combustion engine comprising a crown portion and a skirt portion with a ring-carrying portion between them provided with one or more ring grooves and including an annular chamber behind the ring grooves extending towards or into the skirt por- CTI tion and closed at its lower end, a crown cooling chamber extending across the under surface of the piston crown and communicating with the annular chamber through at least one cooling liquid transfer passage at a point intermediate in the length of the annular chamber and provided with at least one liquid outlet leading into the open interior of the piston, means for coupling the piston to a connecting rod and at least one passage for delivering heat-transfer liquid from the connecting rod into the annular chamber.

2. A piston as claimed in claim l, in which the transfer passage or passages extend from a point in the annular chamber such that the internal volume of the part of the annular chamber lying on the side of that point adjacent to the piston crown is less than half the total volume of the chamber.

3. A piston as claimed in claim 2, in which the passage or passages by which liquid is led from the connecting rod to the annular chamber enters such chamber at a point in its length such that the Volumes of the parts of that chamber lying respectively on the two sides of the point are more nearly equal than the Volumes of the two parts of the chamber lying respectively on the two sides of the point in the chamber from which the transfer passage extends.

4. A piston as claimed in claim 1, in which the crown cooling chamber comprises an annular channel lying adjacent to the circumference of the piston crown, a central pocket lying adjacent to the centre of the piston crown, and a series of channels extending between the annular channel and the central pocket, which channels in association with the annular channel and the central pocket constituting communicating passages between the transfer passage or passages and the outlet or outlets.

5. A piston as claimed in claim 4, in which the transfer passage or passages lead into the central pocket while at least two outlets communicate with the annular channel at circumferentially displaced points therein.

6. A piston as claimed in claim l, in which the crown cooling chamber comprises an annular channel lying adjacent to the circumference of the piston crown, a central pocket lying adjacent to the centre of the piston crown, and a series of channels extending between the annular channel and the central pocket and constituting passages for the flow of liquid from the transfer passage or passages to the outlet or outlets and in which the transfer passage leads from a point in the length of the annular chamber such that the volume of the part of the chamber between that point and the piston crown is less than half the total volume of the chamber.

7. A piston as claimed in claim 6, in which the transfer passage or passages lead into the central pocket and the annular channel is provided with at least two circumferentially displaced outlets.

8. A piston as claimed in claim 1 and comprising a tubular outer part carrying the ring grooves and having a closed end constituting the piston crown, and a plug-like inner part rigidly mounted within the outer part, forming therewith the annular chamber and the crown cooling chamber and having formed therein the transfer passage or passages and the outlet or outlets, means formed 011 the inner parl? for attachment thereof to a `connecting rod by means Qf a gudgecn pin,

6 v REFERENCES CITED The following references are of record in the le of this patent:

5 UNITED STATES PATENTS Number Y' Name Date 2,442,408 Grahm June 1, 1948 2,534,573 Chatterton v Dec. 19, 1950 10 FoREiGN PATENTS Number Country Date 53,352 Sweden June 10, 1920 

